Articles of apparel have been treated with steam for numerous purposes. In the processing of hosiery, one treatment process is preboarding. In preboarding of hosiery, the hosiery is carried on flat forms and subjected to high pressure steam for a period of time in order to set the synthetic fibers making up the hosiery. One type of steam chamber used in preboarding processes is a large cylindrical chamber wherein a large number of forms, for example, twelve double legs forms, are supported on a carriage with their major surfaces facing one another. Such a steam chamber has a relatively large internal volume; for example, 18.5 cubic feet, so that setting times are relatively long; for examle, 23 to 25 seconds at 18 to 20 psi. Low pressure steam treatment is another prior art process used generally with a natural fibers. A flat pressure chamber for use in low pressure steam treatment has recently come into commercial use.
In addition to commercial prior art uses, numerous steam treatment chambers are disclosed in the patent literature. For example, U.S. Pat. No. 2,243,997 issued to Berger, et al., on June 3, 1941, and U.S. Pat. No. 2,811,032 issued to Bellmann on Oct. 29, 1957, disclose textile steam treatment chambers wherein hosiery carried on forms are batch treated within relatively large volume chambers. In both the patents, the forms are collapsed upon one another so that the major surfaces of the forms face one another, and movable doors permit movement into and out of the chamber. The apparatus of the '997 patent is capable of relatively high pressure processing, for example, at 25 psi.
Relatively long and wide steam processing chambers are disclosed in U.S. Pat. No. 2,574,970 issued to Heldmaier on Nov. 13, 1951, and U.S. Pat. No. 2,856,108 issued to Richter on Oct. 14, 1958. In the '108 patent, a plurality of forms are carried on support carriages. A pair of support carriages enter and exit the chamber through doors at the longitudinal ends of the chamber. In the '970 patent, forms carrying hosiery continuously pass through the chamber by means of gap adjusting plates or rollers at either longitudinal end of the chamber.